Using grafted transplants in watermelon production

Authors: ROBERTS, WARREN - OSU, LANE, OK; Bruton, Benny; Fish, Wayne; TAYLOR, MERRITT - OSU, LANE, OK

Submitted to: Georgia Vegetable and Small Fruit Conference and Trade Show Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/7/2006
Publication Date: 1/5/2007
Citation: Roberts, W., Bruton, B.D., Fish, W.W., Taylor, M.J. 2007. Using grafted transplants in watermelon production. In: Kelley, W.T., editor. Proceedings of the 2007 Southeast Regional Vegetable Conference, January 5-7, 2007, Savannah, Georgia. p. 33-36.

Interpretive Summary: Two major influences on watermelon production and marketing have evolved in recent years. They are: (1) additional constraints on watermelon production by diseases and (2) the burgeoning fresh-cut fruit and vegetable market in the U.S. Watermelon diseases appear to be on the rise, in part, because of limited new land for watermelon crop rotation, loss of methyl bromide, and an increased incidence and severity of soil-borne diseases. Furthermore, there is generally insufficient resistance within the watermelon cultivars for adequate control of many soilborne diseases. At the marketing end of the watermelon industry, fresh-cut fruits and vegetables sales have risen to $15 billion annually. Maintaining a high quality fresh-cut watermelon fruit product remains a significant challenge to processors. At the Lane Research Station, Lane, OK, ARS in cooperation with Oklahoma State University, initiated a comprehensive yield, quality, and economic evaluation of grafting watermelon onto gourd or squash rootstocks for both the control of soilborne diseases, yield, and the effect on fruit quality. In 2004, the effect of grafting on sugar content was minimal, the effect of grafting on lycopene content was slightly positive, yields were low in all cultivars, and grafting did increase fruit firmness substantially. Grafted fruit were as much as 2-3 times as firm as the non-grafted commercial standards in the study. In 2005, grafting caused detrimental slightly effects on yield and sugar content, but it caused an increase in fruit firmness in most scion-rootstock combinations. Increased fruit firmness is one of the most important attributes for fresh-cut watermelon. Lycopene content of fruit from grafted plants was equal to, or marginally better than, fruit from non-grafted plants. Lycopene imparts the red color to watermelon and is highly beneficial to human health. Certain combinations of watermelon cultivar and rootstock were significantly superior to other combinations. With a prevalence of root diseases, and restrictions that are currently in place for the use of methyl bromide, grafting may soon become an economically feasible practice for watermelon producers in the U.S.

Technical Abstract: Grafting of watermelon is not new. It has been practiced in other parts of the world for hundreds of years. With a prevalence of root diseases, and restrictions that are currently in place for the use of methyl bromide, grafting may soon become an economically feasible practice for watermelon producers in the U.S. In order to determine the effect of grafting on overall fruit yield and quality, a series of studies was initiated at Lane, Oklahoma in 2004 and 2005 with the cooperative efforts of Oklahoma State University, USDA-ARS, Abbott & Cobb Seed Co., and Speedling, Inc. Twenty five treatment comparisons were made in 2004 and again in 2005. Five scions were grown on their own roots (non-grafted), or were grown on each of four root-stocks. In addition to these 25 treatments, additional comparisons were obtained by planting four non-grafted commercial cultivars. In 2004, the effect of grafting on sugar content was minimal, the effect of grafting on lycopene content was slightly positive, yields were low in all cultivars, and grafting did increase fruit firmness substantially. Grafted fruit were as much as 2-3 times as firm as the non-grafted commercial standards in the study. In 2005, grafting caused detrimental effects on yield and sugar content, but it caused an increase in fruit firmness in most scion-rootstock combinations. Grafting is a technique that may become more practical as other production practices change. Not only does grafting offer the opportunity for introducing disease resistance into desirable watermelon cultivars, but it also may enhance fruit quality. In both years of this study, fruit firmness was increased substantially by grafting. Grafting is widely practiced in many other regions of the world, and we suspect that with time grafting will also become an accepted practice in the United States.